Concepts Of Physics MCQ Edition [Volume 2]PhysicsPhotoelectric Effect and Wave–Particle Duality
During a photoelectric effect experiment, the collector plate is maintained vertically above the emitter plate. A light source is turned on, and a saturation photocurrent is measured. Following this, a vertically downward electric field is switched on.
Options
- AThe photocurrent will increase.
- BThe kinetic energy of the electrons will increase.
- CThe stopping potential will decrease.
- DThe threshold wavelength will increase.
Correct answer
B. The kinetic energy of the electrons will increase.
Step-by-step solution
The collector plate is placed vertically above the emitter plate, so the emitted photoelectrons travel in the upward direction. When a vertically downward electric field E is switched on, the force experienced by an electron of charge -e is F = -e E . Since the electric field is directed downwards, the force on the electrons will be directed upwards. This upward force acts in the direction of motion of the electrons, causing them to accelerate. As a result, the kinetic energy of the electrons will increase as they